Combustion chamber support and igniter



1962 R. J. BARRELLE ETAL 3,048,015

COMBUSTION CHAMBER SUPPORT AND IGNITER Filed July 8, 1959 I /fi' 35 Z/ eif Zi if X? ,'r 351! .55, II 36 I a A w 7*? 5 I I I I zz /p" Z 37 I A;27 7 2/ Z1 z IN VEN T OR.

ATTORNIlY United States Patent )ii' st ws Patented Aug. 7, 19523,048,015 COMBUSTION CHAMBER SUPPORT AND IGNITER Roland J. Barrelle andCharles F. Hayes, Indianapolis, Ind., assignors to General MotorsCorporation, Detroit, Mich., a corporation of Delaware Filed July 8,1959, Ser. No. 825,832 1 Claim. (Cl. 60-39.82)

Our invention is directed to improvements in combustion apparatus suchas is used in gas turbines, and particularly to improvements in supportsfor the combustion liners or flame tubes. In one form of the invention,an improved support for a flame tube is provided. In another form of theinvention, an improved flame tube support and also an improved mountingfor an igniter are provided.

The invention, in either form, is particularly adapted for use withflame tubes which'are supported, in part at least, by members extendingfrom the wall of the air duct in which the flame tube is mounted andpiloted into the wall of the flame tube. The invention in its preferredenvironment as illustrated herein is employed with a flame tubesupported at each end by means other than the improved support of thisinvention, and in which the support according to the invention engagesthe side wall of the flame tube and locates it against movementlongitudinally of the flame tube.

Flame tube installations in which the flame tube is supported bypiloting it on a fuel nozzle at one end and on a turbine nozzle or otherengine structure at the other end are well known. It is also known toprovide a support or locating member extending from the wall of thecombustion apparatus and engaging the liner so as to hold it againstlongitudinal movement. In prior installations of which we are aware, theendwise location has been provided either by an igniter or by aso-called dummy igniter, the dummy igniter being used to locate thoseflame tubes not provided with an igniter.

Such installations have not been entirely satisfactory because of Wearand damage to the combustion liner and the igniter or dummy igniter.These parts are very hot when the engine is operating, and vibration maybe encountered, with the result that the inter-engaging parts may bepounded or worn out of shape and lose their proper fit and suitabilityfor service.

The present invention makes it practicable to use ma terials of greaterstrength and resistance to wear at high temperatures. It also providesfor better cooling of the locating means or support. Where the supportis used in connection with an igniter, the support surrounds the igniterand the igniter is no longer in direct contact with the flame tube. Thesupport includes provisions for cooling the igniter as well as thesupport. The wear of the combustion liner and support is reduced andwear of the igniter which occurred when it served as a support for theflame tube is eliminated. The structure is such that either the igniteror the support may be separately replaced in the event of any damage orfailure of the parts.

It may be pointed out that the materials most suitable to minimize wearof thesupport and combustion liner are not suited for manufacture of theouter shell or casing of igniters. The igniter shell, which projectsintothe flame, is critical from thestandpoint of flame erosion.

The objects of the invention are to improve gas turbine combustionapparatus, to provide improved supports in such apparatus, and toprovide an improved installation of gas turbine igniters whicheliminates wear of the igniter due to mechanical engagement with thecombustion liner and facilitates cooling the igniter.

The nature of the invention and the advantages thereof will be apparentto those skilled in the art from the acparatus embodying the invention.

FIGURE 1 is a partial view of the combustion section of a gas turbineengine of known type, with parts in section on a plane containing theaxis of the engine.

FIGURE 2 is an enlarged view of a portion of FIG- URE 1, showing anigniter installation.

FIGURE 3 is a sectional view taken on the plane dicated by the line 3-3in FIGURE 2.

FIGURE 4 is a sectional view similar to FIGURE 2 showing a supportcorresponding to a dummy igniter installation.

The invention as illustrated is incorporated in an engine of knownconfiguration in which combustion takes place in a number of flame tubesgenerally parallel to and spaced around the axis of the engine. Theseflame tubes are mounted in an annular air duct extending from thecompressor to the turbine of the engine. Since combustion apparatus ofthis general nature is well known, it is not illustrated nor describedin detail herein. Such combustion chamber arrangements in gas turbineengines are illustrated more fully, for example, by U.S. Patents2,861,421 and 2,875,579. Referring to FIGURE 1, the engine in which theinvention is shown comprises a midframe or compressor outlet section 10defining a diffusing passage 11 which discharges into an annular spaceor duct 12 defined by an outer wall or combustion case 13 and an innerwall or shaft housing 14. A number of generally parallel flame tubes 16are mounted within the duct 12. The forward end of one flame tube isillustrated in FIGURE 1. The end of the flame tube is partially closedby a dome or end cap 17 having a central opening which is piloted overthe end of a fuel nozzle 18 suitably fixed to the outer wall of themidframe 10. The rear end of the combustion liner (not shown) may pilotonto the turbine nozzle (not shown) or be otherwise suitably supported.Longitudinal expansion of the flame tube is accommodated by the pilot orslip fits at the ends thereof.

The flame tube may be of any suitable structure but, as illustrated, isa single welded structure composed of a number of rings or sections 19welded together and defining the side wall of the flame tube. An opening21 in the side wall is provided for a crossover tube. Such crossovertubes, as is well known, connect the several flame tubes for propagationof flame between them. A crossover tube as shown in U.S. Patent2,729,938 may be employed.

Ordinarily, two of the flame tubes are provided with are illustrated,for example, in U.S. Patents 2,863,080 and 2,875,365.

Referring to FIGURES 2 and 3, the igniter 20 comprises a generallycylindrical outer shell 22, the inner end portion .23 of which is ofreduced diameter and projects into the flame tube 16. The shell hasfixed thereto, by welding or otherwise, a flange 25 *having holes fortwo cap screws 24 by which it is mounted on a pad 26 welded to thecombustion chamber case 13. The shell 22 is the ground electrode of theigniter, which also includes a high tension electrode 27 mounted withina ceramic insulator 28. The high tension electrode is connected by anelectrical connector 29 of known type to the high tension ignition lead.

The igniter 20 extends into the flame tube through an opening bounded bya cylindrical ferrule 31 welded to the flame tube wall 16 and which isaligned with the pad 26 in the normal position of the flame tube. Ahollow flame tube support 32 comprises a generally cylindrical body 33integral with a flange 34. The body 33 surrounds the outer portion ofthe igniter sleeve, and the flange 34 is held by the cap screws 24between the flange 25 of the igniter and pad 26. The body 33 fits withsmall clearance in an opening 35 in the pad. The body of the support 32is provided with two air inlet holes 36 which receive air from the spacebetween wall 13 and the flame tube. Some of the air flowing into theholes 36 is discharged into the flame tube through an annular space 37defined by a hole in the inner end of the support and the portion 23 ofthe igniter shell.

The igniter shell also defines two cooling air holes 38 approximatelyaligned with the holes 36, which admit air to the interior of theigniter shell. This air flows through the annular space between theshell and the insulator 28 and is discharged into the flame tube. Sincethe general direction of air flowing through duct 12 is from left toright as viewed in FIGURES 1, 2, and 4, air will flow in through theforward holes 36 and 38 and may flow out through the rearward holes 38and 36; but, because of the pressure differential across the flame tubewall, there will be a net flow into the support and igniter and throughthese into the flame tube. This air flow cools both the support and theigniter and cools the ferrule 31 to some extent by conduction into thesupport. It is not necessary to provide dual air inlet holes; but sodoing makes the parts reversible and increases the total cooling airflow around the parts. It will be seen that this installation provides awall or sheath of cooling air over the exterior of the igniter as wellas a cooling air flow through the igniter. With the previousinstallation in which the igniter piloted directly into a ferrule suchas 31, the external flow was not provided.

Also, the present installation isolates the igniter mechanically fromthe flame tube wall or ferrule 31 eliminating fretting and poundingwhich will wear the igniter shell. The igniter shell may be made ofsuperior flame-resistant material without compromises to improve wearresistance.

With the support as described herein, it is possible and desirable tomake both the cylindrical portion 33 of the support and the ferrule 31of a high temperature heat and corrosion resistant material. A materialwhich has been found very suitable for the purpose is a corrosion andheat resistant cobalt-base alloy according to Aeronautical MaterialSpecification AMS-5759 issued February 1, 1956 by the Society ofAutomotive Engineers, Inc. This is a cobalt base alloy containingapproximately 20% chromium, 15% nickel and tungsten.

As to the assembly of the apparatus, the support 32 is inserted throughthe opening in pad 26, in which it fits closely, the igniter plug isinserted through the support and the cap screws 24 are inserted andtightened, holding both the support and the igniter in place. Theigniter may be replaced if desired by removing the cap screws withoutdisturbing the support. If the support is damaged in any way, a newsupport may be provided and the igniter may be reinserted if still ingood condition. As a result of this, a damaged igniter, as, for example,one with a broken insulator, may be replaced and the support beretained. Or, if the sleeve wears after long service and the igniterthen in use is satisfactory, it is not necessary to install a newigniter because of such wear as with the prior art structures in whichthe igniter served as a flame tube support.

FIGURE 4 illustrates a flame tube support as used in those combustionliners '16 which are not provided with igniters. The flame tube 16including ferrule 31 may be identical to and interchangeable with thatpreviously described. The support 40 has the same diameter and length asthe support 32 and is similarly provided with a bolting flange 41 bywhich it is mounted on the pad 26 by cap screws 24. The support 40 isclosed at its outer end and is hollow. An air discharge opening 43 isprovided in the inner end of the support and two cooling air entranceholes 36 are provided, aligned with the direction of air flow as in thesupport 32. A cylindrical tubular member 44- welded to the outer closedend of the support 40 extends downwardly through the internal cavity 42of the support. The member 44 acts as an air deflector or space fillerand concentrates the air flow adjacent the inner wall of the support.

Provision of the air discharge opening 43, by causing air to flowthrough the support into the combustion liner, improves the cooling ofthe support. It also serves to balance the air flow between the variouscombustion liners, since the hole 43 preferably is dimensioned so as topass the same amount of air as that which flows through the outlet 37 ofsupport 33 and through the igniter mounted in it.

It will be seen by those skilled in the art from the foregoing that ourinvention provides a highly desirable arrangement of flame tubesupports, whether or not the support acts in conjunction with anigniter. The invention results in economies in manufacture and greatlyreduces damage to the combustion liners and igniters which are expensiveand diflicult to repair. It also facilitates servicing of the engine.

The description of the preferred embodiment of the invention for thepurpose of explaining the principles thereof is not to be considered aslimiting the invention, since many modifications may be made by theexercise of skill in the art within the scope of the invention.

We claim:

A combustion apparatus comprising, in combination, wall means definingan air duct, a flame tube mounted in the duct having a side walldefining an opening therein and a ferrule fixed to the wall bounding theopening, the wall means having a mounting pad thereon with an openingthrough the pad aligned with the ferrule, a generally cylindrical hollowflame tube support having a flange detachably mounted on the pad, thesupport being piloted in the ferrule, the support having two air inletholes in the side thereof between the wall means and the wall alignedwith the direction of air flow through the air duct and an air dischargehole in the end thereof within the flame tube, and a generallycylindrical igniter slidably mounted within the support and spacedtherefrom to provide an air flow path between the support and theigniter from the inlet holes to the discharge hole, the igniter havingan outer shell with a flange detachably mounted over the flange of thepad, an electrode within and spaced from the outer shell to provide anair flow path therebetween, and having two air inlet holes through theouter shell aligned with the air inlet holes in the support, the igniterprojecting from the support into the flame tube.

References Cited in the file of this patent UNITED STATES PATENTS

